Studies are being conducted to elucidate the epithelial mechanism involved in intestinal fluid loss in infantile soy protein intolerance. The hypothesis is that fluid loss occurs in response to a primary interaction between toxic components of the soybean protein complex and intestinal surface receptors. This interaction is followed by internalization of some component and by fluid secretion into the bowel. Current work has focused on soybean agglutinin, a possible lectin-like effect of glycinin and saponins. The toxicity of these, as well as other fractions, will be investigated in organ culture of intestinal mucosa, in transport preparations of jejunum and ileum in vitro and in vivo using the perfusion technique. The mechanism of interaction will be studied in short term incubations of mucosal tissue and cell-free preparations. Intestinal mucosa from infants with soy protein intolerance, control subjects and experimental animals will be investigated by this approach.